1. Field of the Invention
The invention relates to a grommet of the type fitted around a wire harness and mounted into a panel hole provided in a body panel of a vehicle e.g. an automobile.
2. Description of Background Information
When a wire harness is to be wired from an engine compartment into a passenger compartment, the wire harness is fitted into a grommet made of a rubber or an elastomer, and the grommet together with the harness are passed into a panel hole provided in a partition panel, i.e. a bulkhead, that divides the engine compartment from the passenger compartment. The grommet is thus fitted against the peripheral rim of the panel hole, so that water or dust produced from the engine compartment is prevented from entering into the passenger compartment.
The grommet is therefore made so as to conform with the shape of the panel hole. When the panel hole 3 has an oval shape as shown in FIG. 1A, the grommet used for this panel hole 3 is preferably a cylindrical piece having a cross-section of the same oval shape (oval cylindroid). However, as such a grommet includes stretched oval sections, these parts tend to be deformed toward the inside of the panel hole 3.
To solve such a problem, the enlarged end portion 1a of the grommet 1 may be supported by inside ribs 1b (FIGS. 1B and 1C) as disclosed in Japanese Utility Model published under No. HEI 1-124 612. 
In this manner, the deformation in the stretched oval sections of the grommet 1 may be avoided, thereby preventing an air gap from being formed between the grommet 1 and the panel hole 3. The ingress of water and dust into the passenger compartment can thus be prevented.
However, there have been recently raised problems of noise, as the noise generated in the engine compartment is transmitted into the passenger compartment through the panel hole. There is now a great need for reducing such noise. However, a structure such as a grommet supported by ribs shown in FIGS. 1B and 1C cannot solve noise nuisance problems.
The present invention has therefore been contemplated to solve such problems, and provide an oval-shaped anti-noise grommet, the stretched oval sections of which are designed to avoid being deformed, so that the sealing quality of the grommet is improved, and the noise produced in the engine compartment is effectively sealed off.
To this end, there is provided an anti-noise grommet formed unitarily and in one piece of a suitable elastomer, for example, a rubber, configured to be fitted around a wire harness and mounted into a panel hole with a peripheral rim provided in a vehicle body panel. The anti-noise grommet has a longitudinal axis and a radial direction substantially perpendicular thereto.
The anti-noise grommet includes an inner cylindrical member and an outer cylindrical member. The outer cylindrical member has a small-diameter portion and a larger diameter oval portion sequentially extending therefrom, the outer cylindrical member being mounted concentrically around the inner cylindrical member, thereby forming a first grommet end with the small-diameter portion and a second grommet end with the larger-diameter oval portion.
The anti-noise grommet further includes an oval ring portion including stretched oval sections and arched oval sections, the oval ring portion linking the inner cylindrical member to the outer cylindrical member in the radial direction of the anti-noise grommet at or near the second grommet end.
Each of the stretched oval sections then includes a circumferential central zone and a remaining stretched zone both extending in the radial direction, and the circumferential central zone has a thickness greater than the remaining stretched zone and arched oval sections.
Preferably, the small-diameter portion of the outer cylindrical member includes a round leg portion extending from the first grommet end along the axis, the larger-diameter oval portion includes a flared oval portion extending sequentially from the round leg portion and an oval flange portion extending further sequentially from the flared oval portion, and the oval ring portion links the oval flange portion to the inner cylindrical member.
Preferably yet, the radial direction of the oval ring portion is inclined towards the first grommet end as it extends away from the axis of the anti-noise grommet towards the outer cylindrical member.
Typically, the circular external face of the flared oval portion and oval flange portion is divided by a peripheral slot configured to engage with the peripheral rim of the panel hole.
Suitably, the oval flange portion includes stretched oval sections with a first thickness and arched oval sections with a second thickness, and the stretched oval sections respectively include a circumferential central zone extending along the axis of the anti-noise grommet. The first thickness is greater than the second thickness, and is gradually increased from the arched oval sections towards the circumferential central zone of the stretched oval sections.
More suitably, the first grommet end is configured to be closed with a wire harness by using a closing device, so as to form a closed air gap space.
As the stretched oval sections of the anti-noise grommet are susceptible to receive deformation pressure, that zone of the oval ring portion extending from the circumferential central point of the stretched oval sections to the inner cylindrical member may be reinforced by increasing its thickness. Accordingly, the reinforced zone serves as a support against compressive forces, thus relieving the strain on the outer cylindrical member and maintaining the sealing quality of the anti-noise grommet.
Additionally, when a wire harness is passed through the inner cylindrical member, the wire harness may dilate the latter and press the outer cylindrical member strongly outwardly through the reinforced zone. As a result, the peripheral slot provided in the outer cylindrical member is more firmly engaged with the peripheral rim of the panel hole. The sealing quality of the anti-noise grommet in thus further improved.
Further, the stretched oval sections of the oval flange portion in the outer cylindrical member are made thicker than the arched oval sections. In addition, in the stretched oval sections, the circumferential central zone is made thicker than the remaining zone.
By virtue of this configuration, the outer cylindrical member itself is also reinforced through its stretched oval sections. Deformations in these sensitive sections are thus more reliably prevented.